Question

a) 2.x + 16 =30

b) 2.( x + 1 )³ + 5 = 59

c) x ϵ U (24) và 2 ≤ x ≤ 12

d) ( x - 2 ) : 5 và x ≤ 30

Answer 1

a: 2x+16=30

=>2x=30-16=14

=>x=14/2=7

b: \(2\left(x+1\right)^3+5=59\)

=>\(2\left(x+1\right)^3=54\)

=>\(\left(x+1\right)^3=27\)

=>x+1=3

=>x=2

c: \(x\inƯ\left(24\right)\)

=>\(x\in\left\{1;2;3;4;6;8;12;24\right\}\)

mà 2<=x<=12

nên \(x\in\left\{2;3;4;6;8;12\right\}\)

d: \(x-2⋮5\)

=>\(x-2\in\left\{0;5;10;15;20;25;30;35;...\right\}\)

=>\(x\in\left\{2;7;12;17;22;27;32;...\right\}\)

mà x<=30

nên \(x\in\left\{2;7;12;17;22;27\right\}\)

Answer 2

a) 2.x + 16 = 30

2x = 30 - 16

2x = 14

x = 14 : 2

x = 7

b) 2.(x + 1)³ + 5 = 59

2.(x + 1)³ = 59 - 5

2.(x + 1)³ = 54

(x + 1)³ = 54 : 2

(x + 1)³ = 27

(x + 1)³ = 3³

x + 1 = 3

x = 3 - 1

x = 2

c) x ∈ Ư(20) = {1; 2; 4; 5; 10; 20}

Mà 2 ≤ x ≤ 12

⇒ x ∈ {2; 4; 5; 10}

d) (x - 2) ⋮ 5 nên x - 2 ∈ B(5) = {0; 5; 10; 15; 20; 25; 30; 35; ...}

x {2; 7; 12; 17; 22; 27; 32; 37; ...}

Mà x ≤ 30

⇒ x ∈ {2; 7; 12; 17; 22; 27}

Answer 3

a)2.x+16=30

2.x=30-16

2.x=14

x=14:2

x=7

vậy x=7

b)\(2.\left(x+1\right)^3+5=59\)

\(2.\left(x+1\right)^3=59-5\)

\(2.\left(x+1\right)^3=54\)

\(\left(x+1\right)^3=54:2\)

\(\left(x+1\right)^3=27\)

\(\left(x+1\right)^3=3^3\)

\(x+1=3\)

\(x=3-1\)

\(x=2\)

vậy x=2

c)x∈U(24) và 2≤x≤12

\(x\in\left\{1;2;3;4;6;8;12;24\right\}\)

mà \(2\le x\le12\)

->\(x\in\left\{2;3;4;6;8;12\right\}\)

vậy \(x\in\left\{2;3;4;6;8;12\right\}\)

d)(x-2):5 và x≤30

x≤30 

->\(x=\left\{1;2;3;4;5;6;7;8;...;29;30\right\}\)

->\(x-2=\left\{-1;0;1;2;3;4;5;6....;28\right\}\)

mà x:5

->\(x⋮5\)

->\(x=\left\{5;10;15;20;25\right\}\)

vậy\(x=\left\{5;10;15;20;25\right\}\)